1,2-Diamino-4,5-ethylenedioxybenzene as a highly sensitive fluorogenic reagent for aromatic aldehydes

1,2-Diamino-4,5-ethylenedioxybenzene is shown to be a highly sensitive reagent for aromatic aldehydes, especially for benzaldehydes having a hydroxy group. The reagent reacts selectively with aromatic aldehydes at pH 3.0 (phosphate buffer) within 30 min at 60°C; the products fluoresce most intensely at pH 11. In the manual method, the lower limits of detection vary from 6 pmol ml^?1 to 7 nmol ml^?2. The fluorescent derivatives of aromatic aldehydes can be separated by reversed-phase high-performance liquid chromatography. The fluorescent product from 4-hydroxybenzaldehyde is shown to be 2-(4-hydroxyphenyl)-5,6-ethylenedioxybenzimidazole.     

Diode characteristics of Li3N-diffused ZnSe grown by MOVPE

We have fabricated a ZnSe diode using Li₃N diffusion technique for the purpose of forming p-type ZnSe. The maximum hole concentration in the Li₃N-diffused ZnSe layer, which has been grown on a GaAs substrate by metalorganic vapor phase epitaxy, was as high as 10¹⁸ cm⁻³. The ohmic contact to the p-type ZnSe has been demonstrated and the specific contact resistance of Au/p-ZnSe was 1 × 10⁻² Ω · cm². The Li₃N diffusion technique is useful for the bfabrication of ohmic contacts to p-ZnSe.     

The number and size of branched polymers in high dimensions

We consider two models of branched polymers (lattice trees) on thed-dimensional hypercubic lattice: (i)the nearest-neighbor model in sufficiently high dimensions, and (ii) a spread-out or long-range model ford>8, in which trees are constructed from bonds of length less than or equal to a large parameterL. We prove that for either model the critical exponent for the number of branched polymers exists and equals 5/2, and that the critical exponentv for the radius of gyration exists and equals 1/4. This improves our earlier results for the corresponding generating functions. The proof uses the lace expansion, together with an analysis involving fractional derivatives which has been applied previously to the self-avoiding walk in a similar context.     

On the upper critical dimension of lattice trees and lattice animals

We give a rigorous proof of mean-field critical behavior for the susceptibility (=1/2) and the correlation length (v=1/4) for models of lattice trees and lattice animals in two cases: (i) for the usual model with trees or animals constructed from nearest-neighbor bonds, in sufficiently high dimensions, and (ii) for a class of spread-out or long-range models in which trees and animals are constructed from bonds of various lengths, above eight dimensions. This provides further evidence that for these models the upper critical dimension is equal to eight. The proof involves obtaining an infrared bound and showing that a certain square diagram is finite at the critical point, and uses an expansion related to the lace expansion for the self-avoiding walk.     

Studies on natural antioxidants in citrus species. I. Determination of antioxidative activities of citrus fruits.

The antioxidative activities of twenty types of citrus fruits were investigated with a screening method which is based on rat liver microsomal lipid peroxidation induced by dihydronicotinamide adenine dinucleotide phosphate (NADPH) and adenosine diphosphate (ADP). The activities of the exocarp were greater than those of the sarcocarp and the activities from immature fruits (collected in July-August) were greater than those from mature fruits. The strongest antioxidative activity was found in ponkan (Citrus reticulata Blanco) collected in July.     

Enantiomeric difference in percutaneous penetration of propranolol through rat excised skin.

The percutaneous penetration of R-(+)- and S-(-)-propranolol (PL) through rat excised skin was investigated in vitro. The flux of S-(-)-PL after application to normal skin was high compared with that of R-(+)-PL. On the other hand, in damaged rat skin, the flux of R-(+)-PL was almost equivalent to that of S-(-)-PL. It is suggested that there is an enantiomeric difference between S-(-)- and R-(+)-PL in terms of penetration through rat stratum corneum.     

Visible-light-driven photocatalytic behavior of tantalum-oxynitride and nitride

Tantalum oxynitride (TaON) and tantalum nitride (Ta₃N₅) are investigated in detail as visible-light-responsive photocatalysts. It is found that TaON and Ta₃N₅ evolve H₂ or O₂ via bandgap excitation in the presence of a sacrificial electron donor or acceptor, respectively. These materials exhibit high stability against photo-corrosion under the reaction conditions for H₂ and O₂ evolution. Structural and physical properties of these photocatalysts were also investigated in detail.     

Controllable growth of well-defined regular multiporphyrin array nanocrystals at the water-chloroform interface

On the basis of the coordination geometry of metal ions, regular cubic, clubbed, and wirelike nanocrystals of Cd(2+)-/PtCl(6)(2-)-mediated, and Hg(2+)-/Ag(+)-/PtCl(4)(2-)-mediated multiporphyrin arrays have been grown at the water-chloroform interface. The nanocrystal growth process was monitored by the transmission electron microscopy (TEM), which revealed (1) an intrinsic rule for coordination polymers, that is, the geometries of metal ions (as connects for the coordination polymers) dominate the frameworks of the related polymeric nanocrystals, and (2) one kind of intuitive nanocrystal growth processes at the interfaces. Both electron diffraction and X-ray diffraction patterns indicated the formation of well-defined nanocrystals. It was found that single-/microcrystals were formed at first, and then they grew into polycrystals. The nanocrystal layer was transferred onto Si and quartz substrate surfaces by the Langmuir-Blodgett method, with its composition analyzed by X-ray photoelectron spectroscopy as well as the arrangement of porphyrin macrocycles in the nanocrystals by UV-vis absorption spectroscopy.